Modular pulsed pressure device for the transport of liquid cryogen to a cryoprobe

ABSTRACT

A cryogenic medical device for delivery of subcooled liquid cryogen to various configurations of cryoprobes is designed for the treatment of damaged, diseased, cancerous or other unwanted tissues. The device is a closed or semi-closed system in which the liquid cryogen is contained in both the supply and return stages. The device is capable of generating cryogen to a supercritical state and may be utilized in any rapid cooling systems. As designed, the device comprises a number of parts including a vacuum insulated outer dewar, submersible cryogen pump, baffled linear heat exchanger, multiple pressurization cartridges, a return chamber, and a series of valves to control the flow of the liquid cryogen. The cryogenic medical device promotes the subcooling to any external cryogenic instrument.

RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 61/093,916 filed on Sep. 3, 2008 and titled ModularPulsed Pressure Device for the Transport of Liquid Cryogen to aCryoprobe, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to the medical technology fieldand, in particular, to a medical device for use in a cryogenic system.

BACKGROUND OF THE INVENTION

Over a recent number of years, there has been a strong movement withinthe surgical community toward minimally invasive therapies. The maingoals of the minimally invasive therapies include: 1) eradication oftargeted tissue, 2) decreased hospitalization time, 3) limitedpostoperative morbidities, 4) shortened return interval to dailyfunctions and work, and 5) reduced overall treatment cost. Cryotherapyis a minimally invasive method of treating a disease state throughtissue freezing with thousands of patients now receiving the procedureannually. Currently, cryotherapy is used to treat numerous diseasestates including organ confined tumors such as prostate, kidney, liver,as well as cardiovascular disease, retinal detachment, pain management,and other illness/disease states.

Cryotherapy is an effective yet minimally invasive alternative toradical surgery and radiation therapy. The procedure is done undereither general or epidural anesthesia. Since it is minimally invasive,it offers patients a quicker recovery and reduced severity of potentialside effects. Without the expense associated with major surgery or anextended hospital stay, cryotherapy is a cost-effective treatmentoption.

The approaches utilized to date have focused on the delivery of liquidcryogen through the use of moderate to high pressure on the entiresystem or piston/bellows compression to drive fluid movement. Atpresent, current systems utilizing liquid nitrogen operate at pressuresbetween 14-480 psi; the systems in use cannot operate or withstandpressures greater that 500 psi. Further, the use of heat exchangers havebeen limited to coils placed into a bath of cryogen to allow for timeconsuming, inefficient passive subcooling of the cryogen in whichactivation of these devices circulate a cryogen (such as liquidnitrogen) to a probe to create a heat sink, thus resulting in tissuefreezing.

There exists a need for improvements an cryotherapy, and medical devicesor components associated with the treatment, to better circulate liquidcryogen to a cryoprobe, to provide for rapid delivery through smalltubes, and to facilitate improved measures for treatment and cost. Themedical device of the present invention will allow for the circulation(cooling, delivery, and return) of liquid cryogen to a cryoprobe for thefreezing of targeted tissue. The invention will facilitate theeradication of tissue, decrease hospitalization time, limitpostoperative morbidities, shorten return to daily functions and work,and further reduce the overall treatment cost. Desirably, theseimprovements to device design and application will also increase itsutilization for the treatment of multiple disease states.

SUMMARY OF THE INVENTION

The following invention is a cryogenic medical device designed todeliver subcooled liquid cryogen to various configurations of cryoprobesfor the treatment of damaged, diseased, cancerous or other unwantedtissues. The device is a closed or semi-closed system in which theliquid cryogen is contained in both the supply and return stages.

By converting liquid nitrogen to supercritical nitrogen (SCN) in acylinder/cartridge cooled by atmospheric liquid nitrogen (−196° C.), theSCN can be subcooled and tuned to the liquid phase, attaining an excesstemperature. When the SCN is injected into one or more flexiblecryoprobes, the SCN flows with minimal friction to the tip of the probe.In the tip. SCN pressure drops due to an increased volume and outflowrestriction, heat is absorbed (nucleate boiling) along the inner surfaceof the tip, micro bubbles of nitrogen gas condense back into a liquid,and the warmed SCN reverts to pressurized liquid nitrogen as it exitsthe return tube and resupplies the dewar containing atmospheric liquidnitrogen. This flow dynamic occurs within a few seconds, typically inthe order of 1 to 10 seconds depending on the probe or attachmentconfiguration, and is regulated by a high pressure solenoid valve.Further, the cryosurgical procedure once instruments are in place can beperformed with freeze times in ranges of about 15 seconds to 5 minutes(or ranges thereof), a drastic improvement over current known methods.(Therefore, consecutive freeze times over the course of the entireprocedure significantly reduces time within the medical care setting,reducing overall health costs.) Upon emptying of the first cartridgesubassembly, the process can be repeated with the second cartridgesubassembly or any number of cartridges operated individually or incombination. Furthermore, embodiments of the present invention can beincorporated in any supercooling system or in delivering liquid cryogento the desired instrument.

In one embodiment, the closed or semi-closed system has multiplepressurized cylinders filling and firing in sequence, and pressurizedthrough a heating coil in one or more of the contained pressurizedcylinders. The device is vented to the surrounding atmosphere through anadjustable pressure vent to prevent excess pressure buildup while inoperation. The device comprises a number of parts including a vacuuminsulated outer dewar, submersible cryogen pump, a series ofself-pressurizing pulsatile delivery chambers, baffled linear heatexchanger, return chamber, and a series of valves to control the flow ofthe liquid cryogen. The outer dewar comprises a cryogenic apparatushaving pressurizing pulsatile delivery chambers which drive liquidcryogen through the baffled linear heat exchanger. The linear heatexchanger comprises a tube-within-a-tube (i.e. chamber within a chamberconfiguration) whereby a vacuum is applied to the outer chamber tosubcool an isolated reservoir of liquid cryogen. The inner chambercomprises a series of baffles and a central spiral to increase the flowpath of the liquid cryogen while providing for increased contact-basedsurface area with the outer chamber to allow for more effective heattransfer and subcooling of the cryogen being delivered to the probe.Following circulation to the cryoprobe, cryogen (liquid and gas) isreturned to the device into a return chamber which surrounds the supplychamber, thereby providing for a staged secondary subcooling chamber forthe cryogen in the supply tube. The return chamber is open to the maindewar tank thereby allowing for exchange of liquid and gas between thesupply and return chambers. Device operation is controlled and monitoredby a series of pressure and vacuum valves designed to control the flow,cooling, and pressurization of the liquid cryogen. This control isachieved through various configurations of manual and computercontrolled systems.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read with the accompanying drawing figures. It is emphasized thatthe various features are not necessarily drawn to scale. In fact, thedimensions may be arbitrarily increased or decreased for clarity ofdiscussion.

FIG. 1 is a side view of an illustrative embodiment of the device of thepresent invention.

FIG. 2A is a side view of one embodiment of a heat exchanger of thepresent invention.

FIG. 2B is a cross-sectional view of FIG. 2A, a front view of oneembodiment of a device of the present invention.

FIG. 3A illustrates a side view of one embodiment of a heat exchanger ofthe present invention.

FIG. 3B is a cross-sectional view of FIG. 3A, one aspect of fluid flowthrough one embodiment of a heat exchanger of the device.

FIG. 4 is a top view of one embodiment of a device of the invention.

FIG. 5 is a depiction of a front view of the system.

DETAILED DESCRIPTION

In the following detailed description, for purposes of explanation andnot limitation, exemplary embodiments disclosing specific details areset forth in order to provide a thorough understanding of the presentinvention. However, it will be apparent to one having ordinary skill inthe art that the present invention may be practiced in other embodimentsthat depart from the specific details disclosed herein. In otherinstances, detailed descriptions of well-known devices and methods maybe omitted so as not to obscure the description of the presentinvention.

An external view of a device and system in accordance with oneembodiment of the present invention is shown in FIG. 1. The cryogenicsystem or device 30 has sidewalls 17 which form a container 6 thatencloses an internal cavity, or lumen 15. In an embodiment of FIG. 1,the container 6 takes the form of a vacuum insulated dewar 6. The dewar6 stores liquid cryogen and interconnects a supply line 11 and returnline 12 to a probe or catheter (not shown) to form a closed system 30.The dewar 6 may be made of material such as stainless steel or any othermaterial known for providing a vacuum insulated vessel. The dewar 6 isfilled with liquid nitrogen or other liquefied gas (here, discussing ascryogen) to a maximum level 13. In one aspect, liquid nitrogen may bepreferred. In another aspect, any fluidic cryogen may be utilized (e.g.argon, oxygen, helium, hydrogen).

Within the internal cavity 15 of the dewar 6 is a submersible pump 1which delivers the liquid cryogen to a sealed pressurization apparatus40. In one embodiment, a valve 2 controls the pressure fill intointernal open chamber 42 of the pressurization apparatus 40. Once thecryogen enters the pressurization apparatus 40, an immersion heater 44housed in the internal open chamber 42 heats the cryogen to create adesired pressure. The liquid nitrogen within the pressurized chamberstarts at a temperature of about −196° C. When the heater is activated,it boils the nitrogen within the immediate area. Temperature withininternal cavity 42 therefore stays within about −196° C. to −150° C.more typically in the range of about −196° C. to −160° C., or ratherbetween about −170° C. to −160° C. Pressurized cryogen is then releasedthrough a valve 32 into the baffled linear heat exchanger 4, in oneaspect, liquid nitrogen is converted to supercritical nitrogen (SCN)within the pressurization apparatus. The SCN is then directed to theheat exchanger for subcooling and tuned to the liquid phase to attain anexcess temperature. Thereafter, the SCN can be injected into one or moreflexible cryoprobes such that the SCN flows with minimal friction to thetip of the probe.

The baffled linear heat exchanger 4 in one embodiment is surrounded by asubcooling chamber 3 which subcools the pressurized cryogen for deliveryto external cryoprobes. The subcooling chamber 3 in connection with theheat exchanger 4 at an entrance 23 and an exit opening 36 form anintegral unit 51 for supplying subcooled liquid cryogen. From the heatexchanger 4, the subcooled cryogen passes into a supply line 11 andcontinues out through an exit port 35 and through a control valve 14where various configurations of cryoprobes are attached. The subcoolingchamber may attach a vent line to any of the vents 8, to a supplyconnecting line 19 controlled through a valve 27, or to a vacuum line 16through a control valve 7 which is connected to a vacuum pump 18.

The cryogen is returned (as demonstrated by the arrows in FIG. 1) fromthe cryoprobe via a return tube 12 into a return chamber/cylinder 5 ofthe dewar 6. The return tube 12 connects into the return cylinder 5which also surrounds the supply tube 11 that exits the heat exchanger 4.One or more exit ports 35 may be included in a side wall 17 of the dewar6 or may be a separate unit 14 to incorporate various control valves.

In operation, the device 30 is filled through a supply port 29 and thensealed to form a closed system, thereby allowing for the supply, return,collection, and re-utilization of liquid cryogen during its utilizationin the medical/surgical field. The entire system 30 may or may not bepressurized during operation. The system may also be vented to thesurrounding environment to prevent excess pressure buildup duringoperation. In one aspect, the returning cryogen empties into the returncylinder or chamber 5. In another aspect, the returning cryogen mayempty as bulk fluid into the internal lumen 15 within the dewar 6.

In one embodiment of the present invention, the linear heat exchanger 4subcools the liquid cryogen prior to delivery to tissue. In theembodiment of FIG. 1, the linear heat exchanger 4 is an inner chamber 4which passes through subcooling chamber 3 and is connected via theentrance 23 and exit opening 36. Liquid cryogen passing through theinner chamber 4 is reduced in temperature to a subcooling degree by theouter subcooling chamber 3. The chamber within a chamber configurationincludes a subcooling vacuum chamber 3 filled with liquid cryogen uponwhich a vacuum 18 is drawn through valve-controlled port 9 to reduce theatmospheric pressure on the cryogen. The temperature of the cryogenwithin the subcooling chamber 3 can then be reduced even further. Thesubcooling chamber 3 also comprises valve controlled ports 8 external tothe maximum liquid cryogen level for monitoring and electronicallycontrolling temperatures, pressures, and flow rates of liquid, cryogenpassing through the subcooling unit. In one aspect, a vacuum 18 can bedrawn on vacuum line 16 at a controlled internal valve 7 or externalvalve 9. In another aspect, valve controlled ports 8 may be accessiblefor delivery of liquid cryogen to the subcooling chamber 3 by way of asupply line 19 or as a vent 8 for any excessive gas coming from thesubcooling chamber 3. As depicted in FIG. 1, the vacuum 18 also isattached to the cryoprobe(s) by way of vacuum line 39.

Aspects of the linear heat exchanger 4 are illustrated in FIGS. 2A, 2Band FIGS. 3A, 3B. FIG. 2A and FIG. 3A illustrate side views of differentaspects of a linear baffled heat exchanger 4 and subcooling unit 3 as anintegral unit 51. FIG. 2B depicts a cross-section of FIG. 2A; FIG. 2B isa front view of the linear baffled heat exchanger 4 when looking intothe inner chamber 4. An interior central component or spiral 20 withinthe interior lumen of the chamber 4 operates like a corkscrew toincrease the flow path 25 of the liquid cryogen. An outer wall 22 of theinner chamber 4 also comprises baffles 24 which increase the surfacearea in the heat exchanger for quicker and reduced cooling of the liquidcryogen. As illustrated, a series of baffles 24 emanate into the flowpath 25 (as illustrated by arrows) of the cryogen in the inner lumen,thereby increasing the surface area in the heat exchanger 4. The spiralcomponent, however, may be any size and shape as to efficiently increasethe flow of liquid cryogen. Planar structures, as described below, orany additional features included to increase surface area may beincorporated or substituted.

FIG. 3A illustrates another embodiment of a linear heat exchanger 4 suchthat the internal structure 20 has a planar configuration and alsooperates in a circular motion to increase the flow 25 of the liquidcryogen. FIG. 38 depicts a cross-section of FIG. 3A such that the innertubular unit 21 assists the internal structure 20 in circulating theflow of liquid cryogen through the interior lumen of the chamber 4.

One embodiment of the medical device comprises a return chamber $ whichis illustrated as a return cylinder 5 in FIG. 1 such that the returnchamber 5 surrounds the supply line 11 coming from the heat exchanger 4.The return chamber 5 and the surrounded supply line may then provide asecondary heat exchanger for the system/medical device 30. Cryogenreturn is vented into the return chamber 5. In one aspect, the returnchamber 5 comprises a series of vent holes 26 near the top of the returnchamber 5 to allow for the venting of gas and/or liquid overflow intothe main dewar 6. Vent holes 26 allow for the reutilization of cryogenand thus extend the operation time for the medical device 30.

In another aspect, the return tube 12 is vented into the main dewar 6either directly or by first passing through a linear heat exchanger(similar to the combination of heat exchanger 4 and subcooling chamber3) to subcool the return cryogen prior to venting into the main dewar 6.Return of the cryogen to the main dewar 6 allows the cryogen to returnthrough a heat exchanger such that the cryogen is reutilized and extendsthe operation time even longer.

In another embodiment, the medical device 30 may provide a system whichis controlled through a series of computer controlled valves includingany heaters, sensors, motors, or gauges. The sensors control and monitorpressure, temperature, and fluid level in the dewar, and can measure anymetric as may be desired. In one aspect, the sensors monitor pressurelevels within defined safety ranges. In another aspect, the sensors maycontrol the pressurization of one or more components internal to thedewar. Any of the valves 2, 7, 8, 9, 27 or 32 including exit portalvalve 14, may be automated to enable a controlled and consistentoperation of the cryogenic system (e.g. computer controlled operationthrough the electronically controlled valves).

An embodiment of a system 50 is shown in FIG. 4. As illustrated in a topview of the system 50, a series of six pulsatile pressurization chambers40 are sealed chambers/cylinders 40 within dewar 6 of the closed system50. From the pump, liquid cryogen in pumped to the pulsatilepressurization chambers 40 which then delivers liquid cryogen in acontinuous series of bursts to the heat, exchanger 4. The baffled linearheat exchanger 4 provides an enhanced subcooling of the pressurizedliquid cryogen while also incorporating an integral subcooling unit 3.The chambers 40, each comprising an individual immersion heater 44, canthen sequentially deliver liquid cryogen at consistent rates, or asspecifically determined rates, to the heat exchanger 4.

From the heat exchanger, the subcooled cryogen passes into a supply line11 and continues out through an exit port 35 where a control valve 14 ispositioned and various configurations of cryoprobes are attached. Thecryogen is returned (as demonstrated by the arrows in FIG. 4) via areturn tube 12 from the cryoprobe to the dewar 6 into a return cylinder5. The return tube 12 connects into the return cylinder which surroundsthe supply tube 11 that exits the heat exchanger 4. The entire system 50may or may not be pressurized during operation. The device is alsovented through vent ports 8 to the surrounding environment to preventexcess pressure buildup during operation.

During the operation of the system 50, as illustrated in the embodimentof FIG. 4, a cryogenic system 50 has been filled and detached from itscryogenic fill tank. In one embodiment, the system 50 is a separatemobile unit protected and contained entirely within an enclosed consolefor easy access and mobility. Once the system has been sealed, thecryogenic supply can be maintained for several procedures. Thereutilization of the liquid cryogen provides a time savings andcost-efficient model for cryotherapeutic and cryosurgical procedures.The system 50 can be further utilized for any process requiring rapidcooling.

As depicted, the system 50 comprises a submersible liquid nitrogen pump1 connected to a supply line 11 which directs the liquid nitrogen into asupply manifold 33. The supply manifold 33 routes the liquid nitrogeninto at least one pulsatile pressurization chamber 40 where the liquidcryogen is heated. The pressurized liquid cryogen, here, liquidnitrogen, then starts filling the next pressurization cylinder/chamber40 in the series such that when one chamber 40 is filling, another canbe simultaneously pressurized and prepared for use. This permits a waveof activity through the cylinders so that it can cycle through each stepof system operation. As the pressurized cryogen is delivered to the heatexchanger 4, and passes the subcooled pressurized cryogen out throughthe supply line 11 through the exit port 35 and into the attachedcryoprobes, another pressurization chamber is filled and pressurized.The simultaneous use and pressurization of the liquid cryogen providesfor the sequential delivery of liquid cryogen in a continuous series ofpulsations to a cryogenic instrument or probe.

In one embodiment, liquid nitrogen is used; however, any cryogenic fluidmay be utilized, including nitrogen, argon, helium, hydrogen, and othersuch desired fluids. Each pressurization apparatus 40 comprises apressure valve controlled inlet 52, valve controlled outlet 54, and ventports as may be desired, as well as an immersion heater 44. In oneaspect, the filling of the pressurization apparati 40 is controlledthrough a series of pressure valves 52 on the supply manifold 33. Liquidcryogen is heated within each pressurized apparatus. Pressurized liquidcryogen is then released through the control valve 54 to an outletport/opening 46 of an outlet manifold 34 to the supply line 11, anddelivered to a baffled linear heat exchanger 4. In the illustratedembodiment, a subcooling unit 3 surrounds the heat exchanger 4 for morerapid cooling.

In one embodiment, the cryogenic device 50 comprises six pressurizedapparati 40 linked together. Other embodiments, however, may compriseany number of pressurized apparati 40 individually or linked together incombination. The apparati can then be controlled individually or insequence to deliver pressurized liquid cryogen to the heat exchanger 4.In another aspect, one or more pressurization apparati 40 may bearranged to supply one or more cryoprobes. Further, the series ofpressurized apparati 40 may be interconnected with another series ofapparati 40.

In one embodiment of FIG. 4, six pulsatile pressurization chambers 40are housed within a support network of a console. In one example, threeof the cylinders within one-half of the dewar simultaneously fill whilethree cylinders within the other half of the dewar deliver cryogen outthrough the outlet manifold. (Any number of cylinders, however, may beoperated individually or in desirable combinations.) Liquid cryogen isheated in the sealed pressurization chambers 40. Pressure is increasedto a specified level in the sealed pressurization chambers 40, and thenthe pressurized cryogen is controllably released into a heat exchanger 4to subcool the cryogen. In one aspect, a subcooling vacuum chamber 3surrounds the heat exchanger 4, facilitating the delivery of subcooledcryogen to an attached cryoprobe (also referred to as probe orcatheter). As the pressurized cryogen is utilized, a sensor within theheat exchanger monitors the temperature and pressure of the subcooledcryogen passing into supply line 11, as it continues out through an exitport 35 where various configurations of cryoprobes are attached.

Although the system may fill or discharge each cylinder 40 individually,any simultaneous fill or discharge, or rate of fill or discharge, may beincorporated into the system. The closed system keeps a constant supplyof liquid nitrogen available for delivery to the cryoprobe and providesa more immediate and rapid rate of cooling for cryotherapeuticprocedures. It is therefore possible to close the supply port 29 wheresupply tanks fill the dewar (See FIG. 1 and FIG. 4) and move the systemto any locale or setting. Furthermore, as depicted in FIG. 1, the supplyvalve 2 may be closed and the release valve 14 opened to create a flowof liquid cryogen to the cryoprobe. Various arrangements of valves andsensors may therefore provide for similar flow.

In one embodiment, the pressurized chambers 40 are filled and the dewarsealed. A single drive pump 1 perpetuates directional flow of thecryogen into the pressurization chambers. In one embodiment, allchambers can be filled through various configurations of singledirection pumping. In another embodiment, a reversible pump and fillmethod allows one pressurized chamber 40 to fill and then the pump 1flips or reverses functionality to fill another pressurized chamber.This process can be repeated to fill any number of chambers.

In one embodiment, pressurized chambers 40 are enclosed completelywithin the dewar 6. However, any arrangement of the pressurizedcylinders is possible so long as the closed system provides for thepulsatile delivery of cryogen to the cryoprobe. As such, any single ormultiple configurations of cryoprobes or catheters may be used. Suchinstruments may also include cryogens or cryodevices for rapidcryo-delivery processes or cryotherapies.

As illustrated in FIG. 5, a cryogenic system 60 (also known ascryoengine 60) has a two cylinder configuration, the system of which isdivided into two subassemblies: (I) those components above the cover 61and (U) those components below the cover. All of the components belowthe cover are contained in a liquid nitrogen dewar and immersed inliquid nitrogen at atmospheric pressure (BP=−196° C.) during operation.To understand the operational features of the cryoengine and method ofproduction and transport of supercritical nitrogen (SCN), a briefdescription of cryogen flow follows.

Upon filling the dewar (not pictured) with liquid nitrogen from anexternal source, an immersible liquid cryogen pump 1 is activated tofill each cryogen supply cylinder 2 a & 2 b, or cartridge, sequentially.Initially, one cartridge 2 a is filled along with its linked cryogenpressurization cartridge 3 a. Cryogenic solenoid valves 4 provideventing of the gas within the cartridge assembly to support filling.Upon completion of the filling process, the cryogen pressurizationcartridge 3 a is heated to generate a pressure of about 1000 psi (68bar). Liquid nitrogen becomes critical at about 493 psi (34 bar)(BP=−147° C.). Pressurization beyond the critical point results in theformation of SCN, a dense fluid without surface tension and capable offrictionless flow, and has properties that may be tuned to either a gasor liquid.

By converting liquid nitrogen to SCN in a cartridge cooled byatmospheric liquid nitrogen (−196° C.), the SCN is subcooled and tunedto the liquid phase, attaining an excess temperature (i.e. the abilityto absorb heat without boiling) of approximately 50° C. When the SCN isinjected into the flexible cryoprobe, the SCN flows with minimalfriction to the tip of the probe (boiling chamber). In the tip. SCNpressure drops due to an increased volume and outflow restriction, heatis absorbed (nucleate boiling) along the inner surface of the TIP, microbubbles of nitrogen gas condense back into a liquid, and the warmed SCNreverts to pressurized liquid nitrogen as it exits the return tube andresupplies the dewar containing atmospheric liquid nitrogen. This flowdynamic occurs within a few seconds and is regulated by a high pressuresolenoid valve 4. Upon emptying of the first cartridge subassembly (2 a& 3 a), the process is repeated with the second cartridge subassembly (2b & 3 b).

As demonstrated by FIG. 5, the limitations of liquid nitrogen have beenovercome by developing a novel device to convert atmospheric liquidnitrogen to supercritical nitrogen. Where liquid nitrogen was previouslydelivered through large tubes and did not provide for rapid delivery,the current system herein described allows for rapid delivery of liquidcryogens through very small tubing. The SCN can be injected or drawnthrough two plus meters of hypodermic tubing without boiling, therebyresulting in near instantaneous ice formation at the tip to target sitespecific ablation of tissue as well as the creation of transmurallesions without the formation of a thrombus or aneurysm. Supercriticalnitrogen is a dense fluid with properties of both gas and liquid thatcan be tuned toward one phase or the other. In the liquid phase, SCNlacks surface tension and transports without friction. Theabove-described technology generates SCN in a pressurized cartridgeimmersed in atmospheric liquid nitrogen. This cryoengine, which operatesas a cryogen generator, produces SCN in the liquid phase with a boilingpoint of about −149° C. which is subcooled by the surroundingatmospheric liquid nitrogen to about −196° C. When the SCN is expelledfrom the device to the probe tip, the SCN passes instantly through thesystem without the phase transition to a gas due to both thefrictionless flow and the subcooling which compensates for parasiticheat gain along the path. As such, the embodiment of FIG. 5 may beutilized in any supercooling system or in directing flow of liquidcryogen through to a cryo-instrument. The supercritical point will bedetermined by the chemistry of the specified liquid or gas used.Therefore, the system can be adjusted to accommodate for differences inchemistry.

In utilizing the medical device of the present invention, variousmethods in the industry may be employed in accordance with acceptedcryogenic applications. As discussed, the embodiments of the presentinvention are for exemplary purposes only and not limitation.Advantageously, this device represents an important step in targetedthermal therapies. Various cryosurgical devices and procedures to applyfreezing temperatures to a target tissue may be employed for use withthe medical device of the present invention. The medical device of thepresent invention has been developed to enable and improve some of theapproaches used to target or ablate tissue. Furthermore, the medicaldevice can couple controlled pumping of a liquid cryogen through abaffled linear heat exchanger to decrease the overall temperature of thecryogen providing a greater heat capacity of the fluid and therebyresulting in an increased cooling potential in a cryoprobe.

Thus, the invention facilitates other improvements in cryotherapy, andmedical devices or components associated with the treatment. The medicaldevice of the invention allows for the circulation (cooling, delivery,and return) of liquid cryogen to a cryoprobe for the freezing oftargeted tissue. The invention facilitates the eradication of tissue andcan thereby decrease hospitalization time; and further limitpostoperative morbidities, shorten return to daily functions and work,and further reduce the overall treatment cost. These improvements todevice design and application can also increase utilization of thedevice for the treatment of multiple disease states.

The current device represents an improved development of cryosurgicaldevices by allowing for controlled linear flow of a cryogen without theneed for high pressure or compression based bellows or piston systems.Further, the device contains a novel baffled linear heat exchangerdesigned for cryogen flow through a specialized subcooling chamber.

The embodiments of the present invention may be modified to take theshape of any device, container, apparatus, or vessel currently used inindustry. Specifically, cylindrical or alternative vessels may providecontainers for the cryogenic system for improved cryogenic supply anddelivery. Further, any compartmental arrangement in combination with thecomponents of the above system may take many forms and be of any size,shape, or passageway. Any number of vents may also be utilized tofacilitate operation of the system. The system may also be a partiallyclosed or completely closed system.

In one embodiment of the system, the device is contained within aconsole, a shell or enclosure that allows the system to be easilytransported. The enclosure may then include any mobile feature such aswheels, handles, and fixtures (or allow placement onto a cart havingthese features) so that the system can be transported to and from thelocation of treatment. Such mobility allows the system to be easilymoved to and from an operating room or site of therapeutic treatment. Itis also noted that the system is readily separable from the cryogen filltanks and fill lines that initially supply the system with the liquidnitrogen or other such cryogenic fluid at the supply port 29 (As shownin FIG. 1). This improved feature eliminates the bulkiness of standardcryogenic medical devices.

As presented, the multiple embodiments of the present invention offerseveral improvements over standard medical devices currently used incryogenic industry. The improved cryogenic medical devices remarkablyenhance its utilization for the cooling, delivery and return of a liquidcryogen to a cryoprobe for the freezing of targeted tissue. The presentinvention provides cost savings and significantly reduced treatmenttimes which further reduce expenditures in the healthcare setting. Thepreviously unforeseen benefits have been realized and conveniently offeradvantages for the treatment of multiple disease states. In addition,the improvements enable construction of the device as designed to enableeasy handling, storage, and accessibility. Further uses of the systemoutside of the healthcare setting are foreseeable. Potential uses in thespace industry, defense systems or any industry requiring rapid coolingmay incorporate the cryogenic system as thus described.

As exemplified, the device may include any unitary structure, vessel,device or flask with the capacity to integrally incorporate anycombination of such structures. The invention being thus described, itwould be obvious that the same may be varied in many ways by one ofordinary skill in the art having had the benefit of the presentdisclosure. Such variations are not regarded as a departure from thespirit and scope of the invention, and such modifications as would beobvious to one skilled in the art are intended to be included within thescope of the following claims and their legal equivalents.

1. A method of delivering cryogen to a cryoprobe, said method comprisingthe steps of: providing a device containing cryogen, said device havingone or more ports; providing a pump submersed within the cryogen;providing at least one pressurized apparatus within said device, saidpressurized apparatus having an immersion heater contained therein, atleast one inlet port, and at least one outlet port; providing aninstrument outside said device for use in cooling processes, saidinstrument connected to one or more supply lines which interconnect withsaid device; activating said pressurized apparatus to form pressurizedcryogen; and directing said pressurized cryogen to said instrumentthrough said one or more supply lines.
 2. The method of claim 1, furthercomprising a step of delivering said pressurized cryogen to a heatexchanger prior to said step of directing said pressurized cryogen tosaid instrument.
 3. The method of claim 1, further comprising a step ofsealing said device to form a closed system.
 4. The method of claim 1,wherein said instrument is a cryoprobe utilized in cryotherapeuticprocedures.
 5. The method of claim 1, wherein said step of providingsaid pressurized apparatus comprises a step of arranging two or more ofsaid pressurized apparatuses in series.
 6. The method of claim 5,wherein said step of activating said pressurized apparatus includes astep of pressurizing each of said pressurized apparatuses and releasingsaid pressurized cryogen in a continual series of pulsations.
 7. Themethod of claim 1, further comprising a step of recirculating thecryogen through said device by way of one or more return lines.
 8. Themethod of claim 1, further comprising a step of generating supercriticalcryogen within said at least one pressurized apparatus.
 9. The method ofclaim 1, further comprising a step of generating pressurized cryogenwithin said at least one pressurized apparatus.